Make IF clear.

storage/maria/ma_loghandler.c

@@ -7814,8 +7814,24 @@ void translog_flush_buffers(TRANSLOG_ADDRESS *lsn,
     translog_force_current_buffer_to_finish();
     translog_buffer_unlock(buffer);
   }
-  else if (log_descriptor.bc.buffer->prev_last_lsn != LSN_IMPOSSIBLE)
+  else
+  {
+    if (log_descriptor.bc.buffer->last_lsn == LSN_IMPOSSIBLE)
     {
+      /*
+        In this case both last_lsn & prev_last_lsn are LSN_IMPOSSIBLE
+        otherwise it will go in the first IF because LSN_IMPOSSIBLE less
+        then any real LSN and cmp_translog_addr(*lsn,
+        log_descriptor.bc.buffer->prev_last_lsn) will be TRUE
+      */
+      DBUG_ASSERT(log_descriptor.bc.buffer->prev_last_lsn ==
+                  LSN_IMPOSSIBLE);
+      DBUG_PRINT("info", ("There is no LSNs yet generated => do nothing"));
+      translog_unlock();
+      DBUG_VOID_RETURN;
+    }
+
+    DBUG_ASSERT(log_descriptor.bc.buffer->prev_last_lsn != LSN_IMPOSSIBLE);
     /* fix lsn if it was horizon */
     *lsn= log_descriptor.bc.buffer->prev_last_lsn;
     DBUG_PRINT("info", ("LSN to flush fixed to prev last lsn: (%lu,0x%lx)",
@@ -7824,13 +7840,6 @@ void translog_flush_buffers(TRANSLOG_ADDRESS *lsn,
                      TRANSLOG_BUFFERS_NO);
     translog_unlock();
   }
-  else if (log_descriptor.bc.buffer->last_lsn == LSN_IMPOSSIBLE)
-  {
-    DBUG_PRINT("info", ("There is no LSNs yet generated => do nothing"));
-    translog_unlock();
-    DBUG_VOID_RETURN;
-  }
-
   /* flush buffers */
   *sent_to_disk= translog_get_sent_to_disk();
   if (cmp_translog_addr(*lsn, *sent_to_disk) > 0)